ergonomics
Force. Impact. Reaction.
For every action, there is an equal
and opposite reaction
Perception: better shoes are the only
answer to tired feet
Newton's Third Law of Motion famously states: When one body
exerts a force on a second body, the second body simultaneously
exerts a force equal in magnitude and opposite in direction on the
first body. By the simple act of walking, we subject ourselves to
significant forces every day just by putting foot to floor. Fatigue,
lower back & leg injuries and plantar fasciitis are just some of the
conditions caused, in whole or part, by the forces experienced by
the human body through the foot.
"Underfoot comfort" is often discussed, but has never been
objectively measured. Until now. Numerous studies
going back decades have focused almost entirely on the
measurement of subjective fatigue due to prolonged
standing on different types of floors and mats. In close
cooperation with The University of Pittsburgh
Bioengineering Department, we have developed a test
method designed to measure the direct impact of walking
on the human body. As part of an extensive graduate
study on human fatigue attributed to prolonged standing or
walking on different flooring surfaces, this test method
measures the reduction of Ground Reaction Force (GRF)
of floor covering materials. The test utilizes state-of-the-art
pressure mapping equipment molded into a test shoe that
is free of cushioning and allows the measurement of the
return force imparted on the foot, through the floor
covering, without the variable of footwear.
Figure 2
The GRF being measured through the foot during one complete cycle of walking for
both the left and right foot for two different floor coverings. For reference, the first
spike represents the initial heel strike with the floor.
Figure 1
A representative mapping of the GRF being applied to the foot as detected by
the pressure sensors.
Ground Reaction Force and impact on
the human body
The data
We selected its four most popular floor coverings and
comparatively tested them under identical conditions versus three
other very common resilient floor coverings: 2.5mm linoleum,
2mm sheet vinyl and 2mm 'wood-look' sheet vinyl. Each floor
covering was tested for 50 cycles and the average GRF measured
at the foot was calculated for each. Average GRF is calculated
over one entire cycle of walking, from the time the heel first hits the
floor through to when the foot is lifted from the foor.
The mileage that staff, students, patients and visitors can walk
on any given day has significantly increased over the years.
Campuses grow and facilities expand, so providing spaces that
support good ergonomics is an ever growing challenge decision
makers face as they look to recruit and retain staff, as well as
ensure the safety of patients and students. Musculoskeletal
disorders account for one-third of all occupational injuries
and illnesses reported by employers, constituting the largest
job related injury and illness problem in the United States. Indirect
costs, such as lost productivity, retraining and sick or administrative
time, can be at least 4 to 10 times more than the direct costs.
The results
250
Figure 3
The average GRF as measured on
the different floor coverings over
50 cycles.
GRF of a 216 lb Person
220
Note: Relative reduction in ground
reaction force will vary depending
upon the mass of the person and
the walking gait.
190
The force of a 216 lb person's foot
impacting the floor will be greater
than the 216 lb weight of the person
due to the acceleration of the foot
during walking.
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It is challenging to definitively quantify the impact walking, or just simply standing, on certain surfaces can directly have on the
human body. However, by utilizing the best possible data and evidence, informed decision makers can select those products that
help create the most ergonomically safe environment for their customers and staff.